These blends are chlorine free substitutes (ODP = 0) for R22 as well as for R502 in medium and low temperature ranges.
A composition which was already launched at the beginning of 1992 is known under the trade name Suva® HP62 (DuPont). Long term use has shown good results. Further blends were traded as Forane® FX70 (Arkema) and Genetron® AZ50 (Allied Signal/ Honeywell) or Solkane® 507 (Solvay). HP62 and FX70 have been listed in the ASHRAE nomenclature as R404A and AZ50 as R507A.
The basic components belong to the HFC group, where R143a belongs to the flammable category. Due to the combination with a relatively high proportion of R125 the flammability is effectively counteracted, even in the case of leakage.
A feature of all three ingredients is the very low isentropic compression exponent which results in a similar, with even a tendency to be lower, discharge gas temperature to R502 (R404A/R502 – comparison of discharge gas temperatures of a semi-hermetic compressor). The efficient application of single stage compressors with low evaporating temperatures is therefore guaranteed.
Due to the similar boiling points for R143a and R125, with a relatively low proportion of R134a, the temperature glide with the ternary blend R404A within the relevant application range is less than one Kelvin. The characteristics within the heat exchangers are therefore not very different than with azeotropes. The results obtained from heat transfer measurements show favourable conditions.
R507A is a binary substance combination which even gives an azeotropic characteristic over a relatively wide range. The conditions therefore tend to be even better.
The performance (Comparison of performance data of a semi-hermetic compressor) gives hardly any difference between the various substances and ist very similar to R502. This also explains the high market penetration of these refrigerants. With regard to the thermodynamic properties, they are particularly suitable for commercial medium and low temperature systems.
Typical metallic materials are compatible with HFC refrigerants. Elastomers, however, must be adapted to the changed characteristics. Suitable lubricants are polyol esters (Lubricants for compressors).
The relatively high global warming potential (GWP = 3922 .. 3985), which is mainly determined by the R143a and R125, is something of a hitch. However, it is better than R502 and with regard to the favourable energy demand also leads to a reduction of the TEWI value. Other improvements are possible in this respect due to further developed system control.
Nevertheless, due to their high global warming potential (GWP), the use of R404A and R507A will no longer be allowed in the EU in new installations from 2020. This has been settled in the F-Gas Regulation No. 517/2014 to be applied since 2015. However, the current requirement of phase-down in connection with a strict quota system will lead to an earlier phase-out in many applications. For more detailed information, please refer to BITZER brochure A-510.
In the USA, Canada and Australia there are also requirements to phase-out R404A and R507A. For an international phase-down (starting in 2019) of HCFC and HFC refrigerants, the so-called Kigali Amendment was agreed upon in 2016 as part of the Montreal Protocol.
Alternatives with lower GWP are the HFC blends explained below, as well as HFO/HFC blends being developed and evaluated ("Low GWP" HFOs and HFO/HFC blends as alternatives to HFCs).
Halogen free refrigerants or cascade systems using different refrigerants are also an option for specific applications (Halogen free (natural) refrigerants).
The system technology can be based on the experience with R22 and R502 over a wide area.
On the thermodynamic side, a heat exchanger between the suction and liquid line is recommended as this will improve the refrigerating capacity and COP.
BITZER offers the whole program of reciprocating, scroll and screw compressors for R404A and R507A.
(see also https://www.bitzer.de)
As an alternative to the earlier described substitutes, additional mixtures have been developed based on R32 which is chlorine free (ODP = 0) and flammable like R143a. The refrigerant R32 is also of the HFC type and initially was regarded as a main candidate for R22 alternatives. However, due to extent of blend variations comparable thermodynamic characteristics to R404A/R507A can also be obtained.
These kind of refrigerants were marketed at first under the trade name KLEA® 60/61 (ICI) and are listed as R407A/R407B* in the ASHRAE nomenclature.
Honeywell has developed another blend with the trade name Performax® LT (R407F according to ASHRAE nomenclature) and introduced it into the market, similar Daikin Chemical with R407H. For both blends, the R32 proportion is higher than for R407A, while the R125 proportion is lower. With R407H, this results in certain restrictions for low temperature applications.
However, the necessary conditions for alternatives containing R32 are not quite as favourable compared to the R143a based substitutes discussed earlier. The boiling point of R32 is very low at -52°C, in addition the isentropic compression exponent is even higher than with R22. Rather high proportions of R125 and R134a are necessary to match the characteristics at the level of R404A and R507A. The flammability of R32 is thus effectively suppressed, but the large differences in boiling points with a high proportion of R134a lead to a larger temperature glide.
The main advantage of R32 is the extraordinarily low global warming potential (GWP = 675), so that even in combination with R125 and R134a it is significantly lower than with the R143a based alternatives mentioned above (R407A: GWP = 2107, R407F: GWP = 1825, R407H: GWP = 1490).
Thus, they also comply with the requirement of the new EU F-Gas Regulation which from 2020 will only allow refrigerants of GWP < 2500.
Measurements made with R32 containing blends do show certain capacity reductions compared to R404A and R507A, with low evaporating temperatures. The COP however shows less deviation and is even higher in medium temperature applications (Comparison of performance data of a semi-hermetic compressor).
Whether these favourable conditions are confirmed in real applications is subject to the system design. An important factor is the significant temperature glide, which can have a negative influence upon the capacity/temperature difference of the evaporator and condenser.
With regard to the material compatibility, R32 blends can be assessed similarly to R404A and R507A; the same applies to the lubricants.
Despite the relatively high proportion of R125 and R134a in the R32 blends, the discharge gas temperature is higher than with the R143a based alternatives (especially for R407F and even to a higher degree with R407H). This results in certain limitations in the application range as well as the requirement for additional cooling of compressors when operating at high pressure ratios.
2-stage compressors can be applied very efficiently where especially large lift conditions are found. An important advantage in this case is the use of a liquid subcooler.
* Meanwhile, R407B is no longer available in the market. Due to the historical development of HFC blends this refrigerant will, however, still be considered in this Report.
The experience with R404A/R507A and R22 can be used for plant technology in many respects, although the temperature glide as well as the difference in the thermodynamic properties have to be considered. This especially concerns the design and construction of heat exchangers and expansion valves.
Practical experiences show that qualified conversions are possible. Compared to R22 the volumetric refrigeration capacity is nearly similar while the refrigerant mass flow is only slightly higher. These are relatively favourable conditions for the conversion of medium and low temperature R22 systems.
The main components can remain in the system provided that they are compatible with HFC refrigerants and ester oils.
However, special requirements placed on the heat exchanger with regard to the significant temperature glide must be considered. A conversion to ester oil is also necessary, which leads to increased dissolving of decomposition products and dirt in the pipework. Therefore, generously dimensioned suction clean-up filters must be provided.
Larger differences in thermodynamic properties (e.g. mass flow, discharge gas temperature) and the temperature glide of R407A/F/H may require the replacement of control components and if necessary retrofitting of additional compressor cooling when existing systems are converted.
For newly built systems, a specific design of components and system is necessary.
BITZER offers a comprehensive program of reciprocating and screw compressors for R407A und R407F. An individual selection of compressors for R407H is possible upon demand.
Amongst other aims, R422A (ISCEON® MO79 – Chemours) was developed in order to obtain a chlorine-free refrigerant (ODP = 0) for the simple conversion of existing medium and low temperature refrigeration systems using R22 and R502.
For this, it was necessary to formulate a refrigerant with comparable performance and energy efficiency to that of R404A, R507A, and R22, which also permits the use of conventional lubricants.
R422A is a zeotropic blend of the basic components R125 and R134a with a small addition of R600a. Due to its relatively high R134a percentage, the temperature glide (Refrigerant Properties) lies higher than for R404A, but lower than other refrigerants with the same component blends – such as R417A and R422D (R417A/417B/422D/438A as substitutes for R22).
The adiabatic exponent, and therefore also the discharge gas and oil temperatures of the compressor, are lower than for R404A and R507A. At extremely low temperatures, this can be advantageous. However, in cases of low pressure ratio and suction gas superheat, this can be a disadvantage due to increased refrigerant solution if ester oil is used.
The material compatibility is comparable to the blends mentioned previously, the same applies to the lubricants. On account of the good solubility of R600a, conventional lubricants can also be used under favourable circumstances.
In particular, advantages result during the conversion of existing R22 and R502 systems as mentioned above. However, for plants with high oil circulation rates and/or large liquid charge in the receiver, oil migration might occur – for example if no oil separator is installed.
If insufficient oil return to the compressor is observed, the refrigerant manufacturer recommends replacing part of the original oil charge with ester oil. But from the compressor manufacturer's view, such a measure requires a very careful examination of the lubrication conditions. For example, if increased foam formation in the compressor crankcase is observed, a complete change to ester oil* will be necessary. Under the influence of the highly polarized blend of ester oil and HFC, the admixture of or conversion to ester oil leads to increased dissolving of decomposition products and dirt in the pipework. Therefore, generously dimensioned suction clean-up filters must be provided. For further details, see the refrigerant manufacturer's "Guidelines".
From a thermodynamic point of view, a heat exchanger between suction and liquid line is recommended, improving the refrigerating capacity and coefficient of performance. Besides this the resulting increase in operating temperatures leads to more favourable lubricating conditions (lower solubility).
Due to the high global warming potential (GWP ≥ 2500), R422A will no longer be allowed for new installations in the EU from 2020 onwards. The requirements and restrictions are specified in the F-Gas Regulation 517/2014.
* General proposal for screw compressors and liquid chillers when used with DX evaporators with internally structured heat exchanger tubes. Furthermore, an individual check regarding possible additional measures will be necessary.
BITZER compressors are suitable for R422A. An individual selection is possible upon demand.